looptests.clj

(def v (volatile! nil))

;; a function that I don't think will get disappeared by the compiler:
(defn bla [x]
  (vreset! v x))

(def stuff (vec (range 5e5)))

(defmacro do-reduce [[x coll] & body]
  `(do
     (reduce
       (fn [_# ~x]
         ~@body
         nil)
       ~coll)
     nil))

(time
  (doseq [x stuff]
    (bla x)))

;; ~75 - 80 ms

(time
  (do-reduce [x stuff]
    (bla x)))

;; ~75 - 80 ms

(time
  (dotimes [i (count stuff)]
    (bla (get stuff i))))

;; ~240 - 280 ms

(time
  (loop [i (int 0)]
    (when (< i (count stuff))
      (bla (get stuff i))
      (recur (inc i)))))

;; ~280 - 300 ms

(time
  (let [c (count stuff)]
    (loop [i (int 0)]
      (when (< i c)
        (bla (get stuff i))
        (recur (inc i))))))

;; ~250 - 300 ms

(time
  (loop [i (int (count stuff))]
    (when (not (zero? i))
      (bla (get stuff i))
      (recur (dec i)))))

;; ~390 - 420 ms